1. Field of the Invention
The present invention relates to devices for assisting in the removal of hazardous material such as asbestos, and filtering the hazardous material from the air so that microscopic particles are not released into the atmosphere during the removal process. More specifically, the invention relates to such removal and filtration devices which employ "negative pressure", which as used herein denotes a lower pressure in a containment enclosure than ambient atmospheric pressure.
2. Related Art
Various methods and devices are known in the art for removal of hazardous materials from habitable environments. For example, methods have been developed to remove asbestos (believed to be carcinogenic) in insulation which encloses pipes and other conduits in buildings. The removal of the carcinogenic asbestos must be performed in a safe manner, if microscopic asbestos particles are not to be introduced into the atmosphere, thereby increasing the danger to building occupants rather than reducing it.
A common method of removing asbestos insulation from around pipes has been to enclose a section of pipe within a containment enclosure, sealing the apertures from which the pipe penetrated the bag with duct tape or with wire ties After the containment enclosure was secured about the insulated pipe, measures were taken to attempt to insure that, during the physical removal of the asbestos insulation from the pipe within the containment enclosure, any microscopic particle matter was retained within the containment bag rather than escaping through any hole or seams inadvertently present in the containment bag.
Typically, known methods involve the use of either no negative pressure, or negative pressure created with a HEPA vacuum. The use of HEPA vacuum creates a large amount of negative pressure and air flow volume. The large amount of negative pressure causes the containment bag to totally collapse around the insulated pipe. This collapsing is disadvantageous in that the material cannot be removed from the pipe because the arms of the user may become immobilized. Also, the plastic bag may be drawn against the vacuum hose aperture, causing total cutoff of air flow which puts excess strain on the vacuum motor.
Furthermore, in known systems, there is no way to controllably and accurately vary the vacuum pressure and air flow volume. The comparatively large vacuum in known systems, typically capable of maintaining a pressure of approximately 120 inches of water while moving 100 cubic feet per minute (cfm) possesses many disadvantages. Similarly, known systems are not pressure-adjustable or air flow volume-adjustable, nor are they capable of being delicately controlled or monitored.
High vacuum pressure in known systems places increased stress on the vacuum motor, which may cause burnout of the motor at an earlier time than if lower vacuum pressures were employed. Also, the high vacuum placed stress on the containment enclosure (typically a plastic bag), either resulting in dangerous rupture of weak containment bags or necessitating higher costs of stronger containment bags. Furthermore, the use of such a powerful vacuum requires 110-volt line voltage, causes the unit to weigh too much for true portability, and necessitates the unit to occupy too great a space to be conveniently carried into tight work areas.
Finally, known systems have possessed the disadvantage of unnecessary complexity. Certain systems employing high vacuum pressure air flow have required two apertures, including a first aperture for inputting clean air into the containment bag and a second aperture for allowing the vacuum pump to withdraw contaminated air from the interior of the containment bag through a filter.
Various U.S. patents disclose subject matter which is related to this area of technology. For example, U.S. Pat. Nos. 4,604,111, 4,613,348, 4,626,291, and 4,812,700, all to Natale, disclose containment devices and/or filter devices. U.S. Pat. Nos. 4,783,129 and 4,842,347, both to Jacobson, disclose systems for removal of hazardous waste involving glove bags. Finally, U.S. Pat. No. 953,825 (Gekeler), U.S. Pat. No. 2,741,410 (La Violette), U.S. Pat. No. 4,774,974 (Teter), and U.S. Pat. No. 4,809,391 (Soldatovic) disclose systems for removing asbestos, or devices for supporting the broader function of removing hazardous materials. All documents cited herein are incorporated herein by reference as if reproduced in full in their entirety.
Known systems, taken individually or in combination, have not provided a lightweight, portable, inexpensive means of safely removing hazardous materials. Furthermore, known systems employing negative pressure to prevent escape of hazardous particulate matter have lacked the ability to continuously and reliably monitor and control negative pressure air flow in a flexible containment enclosure, or automatically compensate vacuum pressure by adjusting the speed of the vacuum motor if a leak develops in the containment enclosure or some mechanical malfunction occurs.
Therefore, a need exists for a negative pressure filtration device and method which overcomes the limitations of the known systems.